#include <bits/stdc++.h>
using namespace std;
#define all(x) x.begin(), x.end()
int main() {
vector<basic_string<int>> cc{{}};
basic_string<int> v;
for (int a = 0; a <= 2; ++a) {
cc.emplace_back(v += a);
for (int b = 0; b <= 2; ++b) {
if (b == a) continue;
cc.emplace_back(v += b);
for (int c = 1; c <= 2; ++c) {
if (c != b and not min({a, b, c})) cc.emplace_back(v + c);
}
v.pop_back();
}
v.pop_back();
}
int adj[cc.size()][cc.size()];
for (int i = cc.size(); i--;) {
for (int j = cc.size(); j--;) {
adj[i][j] = cc[j].size();
for (int x = 0, y = 0; y < cc[j].size(); ++y) {
while (x < cc[i].size() and cc[i][x] != cc[j][y]) ++x;
x++ < cc[i].size() and --adj[i][j];
}
}
}
int n;
string a, b;
cin >> n;
cin >> a >> b;
vector dp(cc.size(), n);
for (int i = dp[0] = 0; i < n; ++i) {
vector dp2(cc.size(), n);
for (int j = cc.size(); j--;) {
for (int k = cc.size(); k--;) {
bool c = a[i] - '0';
for (int x: cc[k]) c = x ? x - 1 : c ^ 1;
c == b[i] - '0' and (dp2[k] = min(dp2[k], dp[j] + adj[j][k]));
}
}
dp = move(dp2);
}
cout << *min_element(all(dp));
}
